This invention relates to a tape reel for winding a video tape or an ordinary audio tape, which tape reel is constructed so that the reel is capable of automatically catching firm hold of the inner end of the tape at the time the reel is assembled.
Recently, an increasing proportion of audio and video tape reels have come to be manufactured of plastic materials on account of the ease of molding and the convenience of assemblage. With the exception of ordinary audio cassette tape reels and other similar tape reels, almost all tape reels are provided on the opposite axial end surfaces of the central hubs with flanges having a greater diameter than the aforementioned hubs and it is most convenient to make such reels of plastic materials which by nature enable the tape reels to be easily assembled by the ultrasonic-wave welding technique or the mechanical snap setting technique. If they are made of metallic materials, they require time and labor because their hubs and flanges must be fastened to their reels proper such as with screws.
One example of a tape reel which is specifically designed for the purpose of ensuring simplicity of assemblage has a construction such that one of the two flanges and the hub are either molded integrally or joined in advance and subsequently the remaining separate flange is united with the hub by being applied to and rotated into the opened end of the hub. Structurally, the hub is internally provided with either a step portion formed on the inner wall surface of the hub throughout the entire circumference or cross-piece step portions extending radially from the inner wall to the central portion of the hub and the separate flange is provided with catches formed respectively in externally radial directions or in a circumferential direction, whereby the union of the hub and the flange is attained by rotating the flange relative to the hub to have the catches brought into tight engagement with the step portions (U.S. Patent Application Ser. No. 65,810, filing date Aug. 13, 1979, now U.S. Pat. No. 4,234,137).
As concerns assemblage, such convenient methods as described above have been proposed to the art and improvements such as providing step portions in two levels or designing catches in an unreversible construction have been suggested for the purpose of precluding possible breakage of union due to backward rotation. For the tape reels of this kind, one more important requirement which must not be overlooked is the fact that the inner end of the tape being wound on the reel should be immovably retained on the hub of the reel.
This particular requirement is imposed on video cassette tape reels. With the conventional tape reels, the retention of the inner tape end on the hub entails highly troublesome work and the outcome of the work of retention of the tape end on the reel has an effect upon the accuracy with which the tape is wound on the reel.
From the structural point of view, the device commonly used in the aforementioned conventional tape reel for the fast retention of the inner tape end comprises a dent formed in a radial direction at one portion of the external circumference of the cylindrical hub and a wedge formed in a shape matching the dent, whereby the retention is obtained by overlaying the dent with the inner tape end and subsequently pressing the wedge into tight engagement with the dent across the tape end (U.S. Appl. Ser. No. 65,819, filing date Aug. 13, 1979). This work requires delicate operations and is made more complex by the fact that the work must be carried out in the very small space left between the two opposed flanges already fastened to the hub. Moreover, since the external circumference of the hub around which the inner tape end is to be wrapped includes as a portion thereof the external surface of the wedge, the hub in its complete form tends to be deprived of circularity. This fact has frequently resulted in loss of reel accuracy and consequent occurrence of the phenomenon of wow flutter during the winding and unwinding of the tape on the reel.
These disadvantages are entailed by not only the tape reels of the type described above but also the tape reels of other types, and they mostly originate in the fact that the work of the reel assemblage and the work of the retention of the inner tape end to the hub are performed independently of each other.
An object of the present invention is to provide a tape reel so constructed that the fast retention of the inner end of the tape to be wound on the reel can be attained at the same time that the tape reel is assembled.